1. Field of the Invention
The present invention is directed to constructions for expansion joints for ducting, for example, such as may be used for the exhaust for large stationary gas turbines for the generation of electrical power, and for other ducting environments, especially those involving high temperature and/or substantial flow pulsations or turbulent flow.
2. Prior Art
Ducting which is used to transport air or other gaseous flows that are subject to substantial pulsations or turbulent flow or wide variations in pressure or flow rate, or which has wide variations in temperature range, typically must be provided with expansion joints that will enable the ducting to expand or contract to accommodate such dimensional variations as may be caused by extremes of pressure or temperature variation. In addition, if the ducting is connected to an air or other gaseous flow source that is pulsating, vibrating or in some other form of movement, expansion joints are also necessary in order to accommodate such dimensional changes or movements, without transmitting the stresses, vibrations or movements along the ducting. Otherwise, the ducting might be subject to leakage or failure entirely.
One example of an environment in which such ducting is necessary is that of a stationary gas turbine that is used for electrical power generation. Expansion joints for ducting for gas turbines must be able to accommodate relative axial movements of the duct ends on opposite side of the joint, as well as relative vertical and/or horizontal movements of the duct ends. In addition, such expansion joints must be able to accommodate high temperature gas flows (often in excess of 1000xc2x0 F. at the center of the gas flow).
A joint for use with ducting such as used in association with such moving air or other gaseous flow sources is typically formed by creating a gap in the ducting (which ducting typically may be round or rectangular in cross-section). Inner and outer liner duct structures are then affixed to the opposing duct ends. The inner and outer liner duct structures are typically in overlapping telescopic relation to one another, with the inner liner duct structures on the upstream side of the joint. In this way, the force of the gas flow, during ordinary operating conditions, has less of a tendency to drive the gases between the overlapping portions of the inner and outer liner duct structures. A relatively close fit between the overlapping portions is provided, so that the impact of high-magnitude pulsations or turbulent flow in the air or other gaseous fluid flow, on the remaining surrounding expansion joint structure, is reduced.
To create the fluid-tight seal for the expansion joint, a high-temperature flexible fabric belt is provided to create the flexible outer skin of the expansion joint, connecting the portions of the duct on opposite sides of the gap.
This fabric belt is typically bolted to the opposing duct ends, to flanges that extend outwardly from the duct ends. Typically these flanges are fabricated from steel. These flanges are exposed to the temperatures of the gas flow. In particular, they are exposed to rapid temperature increases, e.g., at the start up of the gas turbine, and can develop tremendous thermal stresses (thermally caused expansion and contraction) that can result in cracking after only a few cycles.
Accordingly, it would be desirable to provide a means for reducing degradation of the fabric expansion joint belt attachment flanges, due to thermal stresses arising from thermal cycling.
This and other desirable characteristics of the present invention will become apparent in view of the present specification, including claims, and drawings.
The present invention is directed, in part, to an expansion joint for flexibly connecting first and second duct ends, the expansion joint having a longitudinal axis and a periphery.
The expansion joint comprises a first frame member, operably connected to, and circumferentially surrounding at least a portion of the first duct end. The first frame member further extends outwardly from the first duct end. The first frame member includes a first attachment web disposed adjacent the first duct end, a flange extending substantially away from the first duct end, and a second attachment web disposed at a position removed from the first duct end, the flange joining the first and second attachment webs.
A second frame member is operably connected to, and circumferentially surrounding at least a portion of the second duct end. The second frame member further extends outwardly from the second duct end. The second frame member includes a first attachment web disposed adjacent the second duct end, a flange extending substantially away from the second duct end, and a second attachment web disposed at a position removed from the second duct end, the flange joining the first and second attachment webs.
A flexible sealing cover peripherally circumferentially surrounds the gap between the first and second duct ends, and affixed to the second attachment webs of the first and second frame members, substantially sealingly connecting the first duct end to the second duct end. At least one of the flanges of at least one of the first and second frame members is provided with at least one convolution therein, for accommodating stresses and strains induced in the respective at least one of the first and second frame members, and permit flexing of said respective at least one of the first and second frame members.
In a preferred embodiment of the invention, the at least one convolution projects substantially longitudinally substantially parallel to the longitudinal axis of the expansion joint.
Preferably, the at least one convolution proceeds circumferentially through the at least one of the first and second frame members.
In an alternative embodiment of the invention, the at least one convolution comprises two or more convolutions in at least one of the first and second frame members.
At least one of the first and second frame members may be monolithically formed. Alternatively, at least one of the first and second frame members is fabricated from separate first and second attachment web members and a flange member.
Preferably, at least one of the first and second frame members has a configuration selected from the following group: rectangular, polygonal, circular, oval.
In an embodiment of the invention, at least one of the first and second frame members generally extends in a plane perpendicular to the longitudinal axis of the expansion joint. In an alternative embodiment of the invention, at least one of the first and second frame members generally extends in a plane oblique to the longitudinal axis of the expansion joint.
The present invention also is directed, in part, to a frame member construction for supporting an end of a fabric expansion joint belt, for an expansion joint for a gas duct of the type wherein first and second duct ends are connected to first and second frame member, each frame member having a first attachment web disposed adjacent a respective duct end, a flange extending substantially away from the respective duct end, and a second attachment web disposed at a position removed from the respective duct end, the flange joining the first and second attachment webs, and wherein end edges of the fabric expansion joint belt are affixed to respective second attachment webs of the first and second frame members. The frame member construction comprises at least one convolution formed in the flange joining the first and second frame members.
In this component of the invention, accordingly to a preferred embodiment of the invention, the at least one convolution projects substantially longitudinally substantially parallel to the longitudinal axis of the expansion joint.
Preferably, the at least one convolution proceeds circumferentially through the frame member.
In an alternative embodiment of the invention, the at least one convolution comprises two or more convolutions in the frame member.
According to one embodiment of the invention, the frame member is monolithically formed. Alternatively, the frame member may be fabricated from separate first and second attachment web members and a flange member.
Preferably, the frame member has a configuration selected from the following group: rectangular, polygonal, circular, oval.
In an embodiment of the invention, the frame member is operably configured to be connected to a duct end and extend generally in a plane perpendicular to a longitudinal axis of the duct end.
In an alternative embodiment of the invention, the frame member is operably configured to be connected to a duct end and extend generally in a plane oblique to a longitudinal axis of the duct end.